Right... well you aint replying quick enough so....

On the back of the stereo you have 2 blocks of connectors.

8 and 7 holes.

1 of them carries the power and the other carries the speaker wires.

In the middle there may be a third block or it may be just a load of pins- the mute is one of these pins

In order to find out which one is the radio mute, you need to earth it - but the safest way is using a test light.

Using your test light just, with the stereo on, just touch the pins in the middle block one at a time.

You'll tell when you've found the mute as the stereo will mute and display phone or mute on the screen.

Connect your mute wire to this pin.